WASHINGTON — A regulatory battle in Washington has compelled professors to ground their research drones, the tiny aircraft academics consider vital for archaeological surveys, river mapping, and countless other discoveries.

The Federal Aviation Administration recently clarified that only hobbyists can fly unmanned aircraft without a special permit. The restrictions aim to improve safety and curb the myriad schemes entrepreneurs have envisioned, from Amazon package drops to pizza deliveries.

But now scholars warn the FAA’s action jeopardizes their work and undermines basic education. The issue lands them in the center of a fight over government’s role in airspace and the appropriate use of drones.

“Aircraft are being defined so broadly that it leaves no space for innovation,” said Paul Voss, an associate professor of engineering at Smith College in Northampton and coordinator of a protest letter signed by nearly 30 researchers, including professors from Boston University and Harvard.

“If you go to Walmart and buy a 15-inch remote-controlled helicopter and use it for fun, it’s a toy,” Voss said. “If you use it for education or research from 4 feet off the grass, it’s an unmanned aircraft system.”

Voss expects to cancel an aerial-vehicle design course this year because students won’t be able to fly prototypes.

Eric Poehler, an assistant professor of classics at the University of Massachusetts Amherst, plans to downsize his archeological project in Pompeii because he can’t teach his students how to use new equipment or test it himself. And Scott Drzyzga, who teaches geography at Shippensburg University of Pennsylvania, won’t get the bird’s-eye view so crucial to his research on the removal of dams from rivers.

The use of commercial drones in US airspace has long bedeviled aviation regulators, who must navigate the intersection of technological innovation, business interests, and public safety.

Recent court rulings have sparked questions about the agency’s ability to enforce bans on these devices. The FAA sought to end some of the confusion in June, when it issued an “interpretation’’ that defined which drones qualify as recreational toys.

Hobbyists, the agency said, can freely fly their remote-controlled airplanes and helicopters as long as the aircraft stay away from airports, keep below 400 feet, and remain within the controller’s sight.

Operators need specific approval for all other purposes, from taking pictures of someone’s property to determining whether a commercial farmer should water his crops.

Researchers contend this unfairly applies to them. They insist, in their letter, that the FAA has expanded its jurisdiction over airspace too far, “including our campuses, private backyards and possibly even inside buildings.”

Public universities, unlike most private colleges, can obtain waivers to use unmanned aerial vehicles (although professors at the University of Massachusetts Amherst and University of Michigan added their names to the FAA letter).

These authorizations can take up to 10 months and are inconsistent, said Benjamin Heumann, director of the Center for Geographic Information Science at Central Michigan University, who uses drones to study wetlands around the Great Lakes.

He still waits for one certificate of authorization from the FAA five months after applying — too late this year to use it.

“It has made it very difficult for us to make plans to conduct our scientific research,” he said, “especially when we receive funding and there is a deadline to collect and analyze data.”

The FAA has received more than 30,000 responses to its recent interpretation and extended a public comment period until Sept. 23. In the meantime, the current regulations stand.

A spokesperson declined to discuss the professors’ specific concerns but said the agency issued “the ‘do’s and ‘don’ts’ to clarify the rules” after “reckless use” of unmanned aircraft in busy areas.

The FAA plans to propose new rules for unmanned aircraft under about 55 pounds in November. It still struggles with a September 2015 deadline set by Congress to open the skies to drones.

Businesses don’t want to wait.

Amazon this year hired a Washington firm to lobby for package deliveries by drone. Google recently bought a producer of solar-powered drones with aims to improve Internet access in remote areas. Even wedding photographers are starting to use unmanned aircraft for that perfect family shot.

Cheaper aircraft options draw interest from realtors, police, journalists, filmmakers, builders, surveyors, and even brewers. The Association for Unmanned Vehicle Systems International estimates the industry will generate $82 billion in economic activity over the next decade.

“The FAA is having problems in basically controlling the introduction of [unmanned aerial vehicles] into air space,” said Philip Finnegan, director of corporate analysis at Teal Group, an aviation consulting firm based in Virginia. “The academic community has sort of gotten caught in the middle.”

Privacy groups also fret about flying objects that see into living rooms or monitor movements.

Senator Edward Markey, a Massachusetts Democrat, introduced a bill last year to prohibit the agency from issuing licenses for drones without describing their purpose. The legislation, which has not made it out of committee, would also require the FAA to create a public website that lists much of that information.

“The use of drones for environmental monitoring and other research holds promise, yet at the same time there are perils from a privacy perspective,” Markey said in a statement to the Globe.

For now, professors are carving chunks from their curricula.

Chris Roosevelt, an associate professor of archeology at Boston University, uses a drone to map excavated ruins in western Turkey, where he does not face the same regulations. Roosevelt wants to teach his students how to operate the tool, but doesn’t see that as an option.

We’re “effectively hamstrung from offering current students, undergraduate and graduate, the proper training they need to even get their feet wet much less master one of the cutting- edge technologies,” he said. “To not offer this to students is a real handicap.”